FIG. 1 depicts a side view of a portion a conventional HAMR disk drive 100. For clarity, FIG. 1 is not to scale. For simplicity not all portions of the conventional HAMR disk drive 10 are shown. The HAMR disk drive 10 includes media 12, a HAMR head 14, and a laser assembly 30. The conventional HAMR head 14 includes a slider 15, a HAMR transducer 20. Although not shown, the slider 15 and thus the laser assembly 30 and HAMR transducer 20 are generally attached to a suspension (not shown). The HAMR transducer 20 includes an air-bearing surface (ABS) proximate to the media 12 during use. The HAMR transducer 12 includes a waveguide 22, write pole 24, coil(s) 26 and near-field transducer (NFT) 28. The waveguide 22 guides light to the NFT 28, which resides near the ABS. The NFT 28 focuses the light to magnetic recording media 12, heating a region of the magnetic media 12 at which data are desired to be recorded. High density bits can be written on a high coercivity medium with the pole 24 energized by the coils 26 to a modest magnetic field.
Although the conventional HAMR disk drive 10 functions, there are drawbacks. The conventional HAMR head 20 may be desired to operate at skew, for example in shingled or other types of magnetic recording. At skew, the HAMR transducer 20 is angled with respect to the track being written. For example, if the pole 24 has a rectangular profile at the ABS, the top and bottom of the rectangle may be at a nonzero angle with respect to the tracks being written. At skew, the region of the media 12 heated by the NFT 28 may be misaligned with the region of the media written by the pole 24. Thus, performance of the HAMR transducer 10 may be adversely affected.
It is noted that early prototypes of a HAMR transducer 20 used a near-parabolic Plain Solid Immersion Mirror (PSIM) as a waveguide 22 to directly heat the media 12 in the absence of the NFT 28. Such a design utilized blue (488 nm) light. The spot size for such a conventional HAMR transducer was reported as one hundred and twenty-four nanometers at full width half max (FWHM). However, such a spot size is not at the theoretical limit of ¼λ for optical systems. Typically, the ¼λ limit refers to the wavelength of light in the optical system. The wavelength of light within the waveguide 22 is λ/n, where λ is the wavelength in vacuum and n is the mode propagation index (a value between the indices of refraction of the waveguide core and its cladding) typically around 1.6 (SiO2 cladding) 1.7 (Al2O3 cladding). For blue light in using such a medium as the waveguide/PSIM, the ¼λ limit would be approximately 59-63 nm. Thus, omitting the NFT 28, such a system may not approach the limit for optical systems. In addition, such a system may still suffer from issues due to skew.
Accordingly, what is needed is an improved HAMR transducer.